Trinisphere and helm of awakening

[chewy01234]

Ok so i play a Helm of Awakening first turn then my opponent drops a trinisphere (sux i know) anyway, I go to cast a mox on my turn does the mox cost 3 or 2?

[wonkey_donkey]

3. Trinisphere takes all things into account that affect cost before then making the cost at least 3 if necessary. If something costs less than 3 to play (whether under a helm or something similar or not) and an untapped trinisphere is in play, it will cost 3.

Tom

[Komatteru]

Correct.  It is impossible for a spell to cost less than 3 when there is a Trinisphere in play.